Chicago Bears rookie Roquan Smith remains unsigned in part because of language in his contract that would allow the team to reclaim guaranteed money if the linebacker is suspended under the NFL's new helmet-contact rules, a source confirmed to ESPN.

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The details of the contract stalemate between Smith and the Bears was first reported by the Chicago Tribune.

Bears first-year coach Matt Nagy confirmed to the Tribune that the helmet rule is "part of the issue" behind Smith's holdout.

Nagy said Monday he was "not surprised" by all the attention the Smith holdout was getting.

Nagy also said he is consulting with Bears general manager Ryan Pace on the negotiations, but said that's standard protocol and that coach and GM are always in constant communication.

Smith's representatives want written assurance in the contract that would prevent the Bears from taking his guaranteed money if he is suspended under the new rule, the Tribune first reported.

But the Bears, according to the Tribune, have not put that financial protection in writing, instead telling Smith's representatives that they will be reasonable in evaluating any situation in which Smith is disciplined under the new rule.